In a system that executes numerical control (NC) of a machine tool by using a numerical control apparatus, it is a general procedure at a time of malfunction occurrence such as alarm warning to log diagnosis information for identifying a cause for the malfunction occurrence. The reason is that the diagnosis information before and after the malfunction occurrence may be necessary for identifying the cause for the malfunction occurrence.
According to a technique disclosed in Patent Literature 1, as an example of a technique for acquiring the diagnosis information before and after the malfunction occurrence, a numerical control apparatus sequentially overwrites and stores the diagnosis information in a circulating memory until a malfunction occurs, and then, when an malfunction occurs, stores the diagnosis information in a logging buffer memory provided separately from the circulating memory.
As another example, Patent Literature 2 discloses a numerical control apparatus in which a logging start condition and a logging end condition are set in advance.